Circuit board assembly with electronic surface mount device and mount arrangement for thermal protection

ABSTRACT

A circuit board assembly includes a circuit board, an electronic surface mount device (SMD), and a spacer that attaches the SMD to the circuit board. A coefficient of thermal expansion (CTE) of the spacer is closer to a CTE of the SMD than a CTE of the circuit board. The circuit board assembly also includes a flexible electrical lead that extends between and that is electrically connected to the SMD and the electrical node of the circuit board. Methods of manufacturing the circuit board assembly include selectively heating joining material at a predetermined heating rate and selectively cooling the joining material at a predetermined cooling rate to attach the flexible electrical leads to the SMD and the circuit board.

TECHNICAL FIELD

The present disclosure generally relates to circuit board assemblieswith electronic surface mount devices and, more particularly, relates tocircuit board assemblies with an electronic surface mount device (SMD)and a mount arrangement for thermal protection of the SMD. Systems andmethods of manufacturing these circuit board assemblies are alsodisclosed.

BACKGROUND

Circuit board assemblies often include a printed circuit board and aplurality of electronic surface mount devices (SMDs), such ascapacitors, resistors, etc. that are mounted directly to the surface ofthe printed circuit board. These assemblies are used in a wide varietyof devices.

However, there may be difficulty in manufacturing these circuit boardassemblies without inducing internal stresses and/or causing thermalshock to the SMD. Likewise, because the circuit board and the SMD oftenhave largely different coefficients of thermal expansion, there may bedifficulty in avoiding thermal shock to the SMD during the operatinglife of the circuit board assembly. Repair and replacement of SMDs onexisting circuit board assemblies may also present difficulties due tothe thermal sensitivities of the SMDs.

Accordingly, there remains a need for an improved SMD mount arrangementthat reduces thermal stresses on the SMD during manufacture and/or useof a circuit board assembly. There are also needs for improvedmanufacturing methods and systems for making the same. Other desirablefeatures and characteristics of the present disclosure will becomeapparent from the subsequent detailed description and the appendedclaims, taken in conjunction with the accompanying drawings and theforegoing technical field and background.

BRIEF SUMMARY

In one embodiment, a method of manufacturing a circuit board assembly isdisclosed. The method includes attaching a flexible electrical lead toan electronic surface mount device (SMD) with a joining material,including selectively heating the joining material at a predeterminedheating rate and selectively cooling the joining material at apredetermined cooling rate. The method also includes attaching the SMDto a mount area of a circuit board using a spacer that is interposedbetween the mount area and the SMD. The spacer spaces the SMD at adistance from the mount area. A coefficient of thermal expansion (CTE)of the spacer is closer to a CTE of the SMD than a CTE of the circuitboard. Moreover, the method includes attaching the flexible electricallead to an electrical node of the circuit board.

In another aspect, a circuit board assembly is disclosed that includes acircuit board with a mount area and an electrical node. The circuitboard assembly also includes an electronic surface mount device (SMD).The circuit board assembly further includes a spacer that attaches theSMD to the mount area of the circuit board and that spaces the SMD at adistance from the mount area. A coefficient of thermal expansion (CTE)of the spacer is closer to a CTE of the SMD than a CTE of the circuitboard. Moreover, the circuit board assembly includes a flexibleelectrical lead that extends between and that is electrically connectedto the SMD and the electrical node of the circuit board.

In a further aspect, a manufacturing system for manufacture of a circuitboard assembly is disclosed. The system includes a fixture that supportsan electronic surface mount device (SMD), a flexible electrical lead,and a joining material together. The system also includes a temperaturecontrol unit that selectively controls a temperature of the joiningmaterial while the fixture supports the SMD, the electrical lead, andthe joining material. The temperature control unit is configured toselectively heat the joining material at a predetermined heating rate tomelt the joining material, and to selectively cool the joining materialat a predetermined cooling rate to re-solidify the joining material,thereby attaching the SMD and the electrical lead. The temperaturecontrol unit is configured to selectively melt and re-solidify a nodematerial of a circuit board while the SMD is attached to a spacer thatis interposed between the SMD and the circuit board. The temperaturecontrol unit is configured to selectively heat the node material at thepredetermined heating rate to melt the node material, and to selectivelycool the node material at the predetermined cooling rate to re-solidifythe node material, thereby attaching the electrical lead to anelectrical node of the circuit board with the spacer spacing the SMD ata distance from a mount area of the circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and wherein:

FIG. 1 is a perspective view of a circuit board assembly according toexample embodiments of the present disclosure;

FIG. 2 is a flowchart illustrating a method of manufacturing the circuitboard assembly of FIG. 1; and

FIG. 3 is a perspective view of a SMD, electrical leads, and othercomponents shown during manufacture of the circuit board assembly ofFIG. 1;

FIG. 4 is a longitudinal section view of components of a manufacturingsystem for joining the components of FIG. 3;

FIG. 5 is a side view of the components of FIG. 3 shown attachedtogether;

FIG. 6 is a perspective view of a circuit board and a spacer shownduring manufacture of the circuit board assembly of FIG. 1; and

FIG. 7 is a side view showing the components of FIG. 5 being attached tothe circuit board and spacer of FIG. 6.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the present disclosure or the application and usesof the present disclosure. Furthermore, there is no intention to bebound by any theory presented in the preceding background or thefollowing detailed description.

Referring to FIG. 1, a circuit board assembly 100 is shown according toexample embodiments of the present disclosure. Those having ordinaryskill in the art will appreciate that the circuit board assembly 100 ofFIG. 1 may constitute a part of a larger electrical circuit of a printedcircuit board assembly. In some embodiments, the circuit board assembly100 may be incorporated within a control system of an aircraft or othervehicle; however, it will be appreciated that the circuit board assembly100 may be incorporated within other electrical systems withoutdeparting from the scope of the present disclosure.

The circuit board assembly 100 may generally include a circuit board102, an electronic surface mount device (SMD) 104, and a mountarrangement 106. The SMD 104 may be one of a variety of devices, such asa capacitor, a resistor, etc. The SMD 104 may be a known device that istypically mounted directly to the board 102. However, in embodiments ofthe present disclosure, the mount arrangement 106 may support the SMD104, mechanically attach it to the circuit board 102, and maintain theSMD 104 separated at a distance from the circuit board 102. Also, themount arrangement 106 may electrically connect the SMD 104 withincircuitry of the circuit board 102.

Furthermore, the mount arrangement 106 may protect the SMD 104 fromdamage due to thermal conditions. Specifically, the mount arrangement106 may protect the SMD 104 against stress and/or fracture due todifferences in thermal expansion between the SMD 104 and the circuitboard 102. Also, because of the mount arrangement 106, installation ofthe SMD 104 onto the circuit board 102 is unlikely to impart internalstresses on the SMD 104.

The mount arrangement 106 also facilitates manufacture of the circuitboard assembly 100. The mount arrangement 106 may be used in newlydesigned assemblies 100. The mount arrangement 106 may also be used whenrepairing and replacing SMDs 104 on conventional circuit boardassemblies 100.

The circuit board assembly 100 will now be discussed in detail accordingto example embodiments. It will be appreciated that the circuit boardassembly 100 may vary from those shown and described without departingfrom the scope of the present disclosure.

The circuit board 102 may be a printed circuit board that is relativelyflat and thin. The circuit board 102 may be a printed circuit board witha top surface 116 and a bottom surface 118. The top surface 116 mayinclude a plurality of electrically conductive traces 117 thatelectrically connect the SMD 104 into a larger circuit. One exemplarytrace 117 is shown in FIG. 1 and extends to a through-hole 119 of thecircuit board 102. The through-hole 119 may extend from the top surface116 to the bottom surface 118. An electrically conductive vertical trace121 may define the through-hole to provide an electrical path betweenthe SMD 104 and traces and/or other circuit elements supported on thebottom surface 118. The top surface 116 may also define a mount area120. The mount area 120 may be relatively flat and smooth. In FIG. 1,the mount area 120 is substantially rectangular. The top surface 116 mayadditionally include electrical nodes, such as a first node 122 and asecond node 124, which are spaced apart horizontally with the mountareas 120 disposed therebetween. The nodes 122, 124 may be flat,rectangular plates (i.e., electrode pads, etc.) made of conductivematerial. As shown in FIG. 1, the second node 124 may be disposed at oneend of the trace 117 and spaced apart from the through-hole 119. Thus,the trace 117 and the vertical trace 121 may electrically connect thesecond node 124 within the electrical circuit of the assembly 100.Although not shown, the first node 122 may have respective traces 117,121 (and a respective through hole 119) for electrically connecting thefirst node 122 within the circuit of the circuit board assembly 100. Thetraces 117, 121 and the nodes 122, 122 may be made of a knownelectrically conductive material.

The SMD 104 may be cuboid in shape and may include a top side 126 thatfaces away from the circuit board 102 and a bottom side 128 that facestoward the circuit board 102. The SMD 104 may also include electricalterminals, such as a first terminal end 130 and a second terminal end132, which are disposed on opposite horizontal sides of the SMD 104 andwhich extend generally in the vertical direction with respect to thecircuit board 102. As such, the SMD 104 may be a so-called “leadless”SMD 104 (i.e., without leads) in some embodiments. In some embodiments,the SMD 104 may be a capacitor, such as a multi-layer ceramic chip(MLCC) capacitor. Accordingly, the SMD 104 may include a plurality oflayers 134. The layers 134 may be substantially flat and planar andarranged in overlapping, layered arrangement. The SMD 104 may bearranged with the layers 134 substantially parallel to the top surface116 of the circuit board 102. The layers 134 may be made primarily froma ceramic material. In some embodiments, the coefficient of thermalexpansion (CTE) of the SMD 104 may be between seven (7) ppm/° C. andeleven and one-half (11.5) ppm/° C. Also, the SMD 104 may be relativelyrigid and inflexible. Also, it will be appreciated that the SMD 104 maybe a leadless component with the terminal ends 130, 132 providingelectrical connection for the layers 134 of the SMD 104.

As mentioned above, the SMD 104 may be mechanically supported on thecircuit board 102 and electrically connected within the respectivecircuit via the mount arrangement 106. In some embodiments, the mountarrangement 106 may generally include a spacer 108. Also, in someembodiments, the mount arrangement 106 may include one or more flexibleelectrical leads, such as a first lead 110 and a second lead 112.

The spacer 108 may be cuboid in shape and may include an upper side 140and a lower side 142. The spacer 108 may have a substantially constantthickness such that the upper side 140 and the lower side 142 aresubstantially parallel. In some embodiments, the thickness of the spacer108 (measured between the upper side 140 and the lower side 142) may bebetween approximately 0.050 inches and 0.060 inches; however, thethickness may be different from these embodiments. The thickness of thespacer 108 may be chosen based on the dimensions of the other componentsand/or space availability. Furthermore, the thickness of the spacer 108may be chosen to facilitate attachment of the leads 110, 112. Moreover,the thickness of the spacer 108 may be selected so that the spacer 108provides predetermined thermal performance. The lower side 142 of thespacer 108 may face the circuit board 102, and the upper side 140 mayface the SMD 104. The lower side 142 may overlay (i.e., may be layeredflat over) the mount area 120 of the circuit board 102. The lower side142 may be bonded and attached to the mount area 120 of the circuitboard 102 with the upper and lower sides 140, 142 parallel to the topsurface 116. The bottom side 128 of the SMD 104 may overlay and may belayered flat over the upper side 140 of the spacer 108. Accordingly, thespacer 108 attaches the SMD 104 to the mount area 120 of the circuitboard 102 and spaces the SMD 104 at a distance 144 from the mount area120.

The spacer 108 may be made from a stiff, strong, and rigid material,such as a ceramic. The spacer 108 may be made from a ceramic material,such as alumina ceramic (Aluminum Oxide), in some embodiments. Thecoefficient of thermal expansion may be between approximately seven (7)ppm/° C. and eleven and one-half (11.5) ppm/° C.

In some embodiments, the spacer 108 and the SMD 104 may exhibit similarmaterial characteristics. The spacer 108 and the SMD 104 may be selectedand constructed to exhibit similar thermal characteristics. In someembodiments, the spacer 108 and the SMD 104 may have substantiallysimilar coefficients of thermal expansion (CTE). Stated differently, thespacer 108 and the SMD 104 may have CTEs that fall within apredetermined range or percentage of each other. For example, the spacer108 CTE may be at least 60% of the CTE of the SMD 104. Additionally, theCTE of the spacer 108 may be, at most, equal to the CTE of the SMD 104.In some embodiments, the CTE of the spacer 108 may be lower than the CTEof the SMD 104 and within the predetermined range. Also, as will bediscussed, the CTE of the spacer 108 may be closer to the CTE off theSMD 104 than the CTE of the circuit board 102. The CTE of the spacer 108and SMD 104 may be significantly lower (e.g., an order of magnitudelower) than that of the circuit board 102 in some embodiments.

In some embodiments, the SMD 104 may be formed with a ceramic materialsuch that the CTE of the SMD 104 is between approximately 9.5 to 11.5ppm/° C. In addition, the spacer 108 may be formed of Alumina such thatthe CTE of the spacer 108 is approximately 7 ppm/° C. Thus, in theseembodiments, the CTE of the spacer 108 is approximately 61% of the CTEof the SMD 104. Because of the relative similarity of CTEs, and becausethe SMD 104 is spaced away from the circuit board 102, thermal loadsfrom the circuit board 102 onto the spacer 108 are unlikely to transferto the SMD 104.

Furthermore, it is known that ceramics (like those of the SMD 104) areless likely to fracture under compression loads in comparison withtensile loads. In the above embodiments, the CTE of the spacer 108 isslightly lower than that of the SMD 104. Thus, even if the SMD 104thermally expands at a slightly higher rate than the spacer 108, thespacer 108 may impart compressive stress on the SMD 104. Such loading islikely to be minimal. As such, the SMD 104 may better withstand thermalloads during manufacture and/or during the installed, operating life ofthe SMD 104.

In additional embodiments, the spacer 108 and the SMD 104 may beconstructed from the same material to exhibit similar thermal behaviorin some embodiments. For example, a majority of both the spacer 108 andthe SMD 104 may be constructed from alumina ceramic (Aluminum Oxide) insome embodiments.

In some embodiments, the surface area of the bottom side 128 may belarger than the surface area of the upper side 140 such that the SMD 104overhangs the spacer 108. As shown in the embodiment of FIG. 1, the SMD104 may have a first overhanging portion 136, which overhangs one sideof the spacer 108. The first overhanging portion 136 may include thefirst terminal end 130 and part of the layered portion of the SMD 104.Also, the SMD 104 may have a second overhanging portion 138, whichoverhangs the opposite side of the spacer 108. The second overhangingportion may include the second terminal end 132 and another part of thelayered portion of the SMD 104.

Accordingly, the spacer 108 of the mount arrangement 106 may providestrong and rigid support for the SMD 104 on the circuit board 102. Also,the spacer 108 may provide thermal protection for the SMD 104. Forexample, if the SMD 104 and the circuit board 102 thermally expand atdifferent rates, the spacer 108 may limit transfer of stress to the SMD104 and prevent internal stresses from being imparted onto the SMD 104.

Furthermore, the mount arrangement 106 may include the first lead 110and the second lead 112. The leads 110, 112 may be flexible. The leads110, 112 may include and/or may be constructed from conductive material.The leads 110, 112 may be formed from and/or may include annealed copperin some embodiments to provide high flexibility and electricalconductivity for the leads 110, 112.

The leads 110, 112 may be substantially similar except that the firstlead 110 extends between and electrically connects the first terminalend 130 and the first node 122 whereas the second lead 112 extendsbetween and electrically connects the second terminal end 132 and thesecond node 124. Features of the second lead 112 discussed below mayalso be included as features of the first lead 114.

The lead 112 may be a relatively flat and elongate strap (i.e., band,strip, flap, belt, etc.) of conductive material with an outer side 170and an inner side 172. The lead 112 may have a thickness (measuredbetween the outer and inner sides 170, 172) between 0.002 and 0.004inches. Also, the lead 112 may extend longitudinally between the secondterminal end 132 of the SMD 104 and the node 124 of the circuit board102. More specifically, the lead 112 may include a device connection end150, which is layered on, overlapped over, and attached (mechanicallyand electrically) to the second terminal end 132 to define a firstconnection 156 (first electrical connection of the circuit boardassembly 100). As such, the outer side 170 faces the second terminal end132 at the first connection 156, and the inner side 172 faces away fromthe second terminal end 132 at the first connection 156. Moreover, thedevice connection end 150 may extend in the vertical direction relativeto the top surface 116 of the circuit board 102 at the first connection156. The lead 112 may also include a board connection end 152, which islayered on, overlapped over, and attached (mechanically andelectrically) to the second node 124 to define a second connection 158(second electrical connection of the circuit board assembly 100). Assuch, the outer side 170 faces the second node 124 at the secondconnection 158, and the inner side 172 faces away from the second node124 at the second connection 158. Moreover, the board connection end 152may extend in the horizontal direction (across the circuit board 102 andsubstantially normal to the device connection end 150) relative to thetop surface 116 of the circuit board 102 at the second connection 158.The lead 112 further includes an intermediate portion 154 that extendsbetween the device connection end 150 and the board connection end 152.

The intermediate portion 154 may extend nonlinearly between theconnection end 150 and the board connection end 152 in some embodiments.Also, one or more segments of the intermediate portion 154 may curve(contour) gradually from the device connection end 150 and the boardconnection end 152 as shown in FIG. 1. For example, the intermediateportion 154 may extend vertically away from the device connection end150 and the circuit board 102. The intermediate portion 154 may alsoinclude a first bend 160 that is proximate the device connection end150. The first bend 160 may be an approximately one-hundred-eightydegree (180°) gradual, nonlinear contoured bend 160 such that theintermediate portion 154 extends vertically away from the deviceconnection end 150 and returns toward the circuit board 102 and theboard connection end 152. The intermediate portion 154 may furtherinclude a second bend 162 that is proximate the board connection end152. The second bend 162 may be an approximately ninety degree (90°)contoured bend 162 such that the intermediate portion 154 extendshorizontally along the circuit board 102 and toward the board connectionend 152. As shown, the device connection end 150 may be disposeddirectly above and may extend transverse relative to the boardconnection end 152. Also, the board connection end 152 may be disposedbetween the device connection end 150 and the circuit board 102 in thevertical direction. Accordingly, the circuit board assembly 100 may becompact due to the overlapping and transverse arrangement of the boardconnection end 153 and the device connection end 152.

Also, the intermediate portion 154 may extend freely between the deviceconnection end 150 and the board connection end 152. In other words, theintermediate portion 154 may be free of and unattached from the SMD 104and the circuit board 102.

Accordingly, the intermediate portion 154 may resiliently flex, forexample, in response to thermal expansion and/or contraction of thecircuit board 102. This may occur when the circuit board assembly 100 isinstalled and operational. For example, in some embodiments, the circuitboard assembly 100 may be part of a space vehicle and used in-orbitwhere ambient temperatures cyclically fluctuate, causing the circuitboard 102 to thermally expand and contract. The leads 110, 112 mayresiliently flex in response to this thermal expansion/contractionwithout imparting stress on the SMD 104. The circuit board 102 may alsothermally expand/contract during manufacture of the assembly 100. Forexample, solder or other conductive material may be melted andre-solidified during manufacture of the circuit board assembly 100,and/or during manufacture of the larger assembly that includes thecircuit board assembly 100, causing the circuit board 102 to thermallyexpand and contract. The leads 110, 112 may resiliently flex in responseto this thermal expansion/contraction of the circuit board 102 withoutimparting stress on the SMD 104.

Additionally, the intermediate portion 154 may resiliently flex toprotect the SMD 104 under other types of loads as well. For example, theintermediate portion 154 may flex due to vibration of the circuit board102.

The leads 110, 112 and the spacer 108 of the mount arrangement 106 maywork in concert to protect the SMD 104 from damage. As stated, the leads110, 112 may resiliently flex in response to a thermal load withoutimparting stress on the SMD 104. In addition, the spacer 108 may providestrong and rigid support for the SMD 104 while also providing thermalprotection for the SMD 104. For example, if the SMD 104 and the circuitboard 102 thermally expand at different rates, the spacer 108 may limittransfer of stress to the SMD 104 and prevent internal stresses frombeing imparted onto the SMD 104. The spacer 108 may withstand thermalloading at the mount area 120 and avoid transferring this stress to theSMD 104, thereby providing protection from such thermal loading. Thus,even if the SMD 104 is sensitive to thermal shock, the mount arrangement106 may protect against damage, and the mount arrangement 106 may behighly robust. Moreover, the SMD 104 may be protected from mechanicalstress from deflections of the circuit board 102 (e.g., due to vibrationloads). There is a reduced amount of area of the SMD 104 in contact withthe circuit board 102, which results in a reduced amount of deflectionarea of the circuit board 102. Also, the leads 110, 112 may deflect dueto vibration of the board 102 without imparting stress on the SMD 104.

Referring now to FIGS. 2-7, a method 200 of manufacturing the circuitboard assembly 100 will be discussed according to example embodiments.As will be discussed, a manufacturing system 300 of the type representedin FIG. 4 may be used according to the method 200 for manufacturing thecircuit board assembly 100 of the present disclosure. In someembodiments, one or more aspects of the method 200 may be performedmanually (by hand). In additional embodiments, one or more aspects ofthe method 200 may be performed automatically. In the latterembodiments, the manufacturing system 300 may include a control system400 (FIG. 4) for controlling one or more actuators, handling devices,temperature control unit(s), etc. for handling, moving, arranging,heating, and/or cooling the components of the circuit board assembly100. The control system 400 may be a computerized system with hardwareand software comprising one or more processors, sensors, computerizedmemory units, user input/output devices, etc. The control system 400 mayreceive input (e.g., from sensors), process the input, and generatecontrol commands that are output to the actuators, heaters, coolers,and/or other components of the manufacturing system 300.

As shown in FIGS. 2 and 3, the method 200 may begin at 201, where theSMD 104, a first lead preform 180, a second lead preform 182, a firstsolder preform 190, and a second solder preform 192 are provided. Asrepresented in FIG. 3, the first and second lead preforms 180, 182 maybe elongate, flat straps (bands, strips, flaps, belts, etc.) that extendlinearly. As will be discussed, the first lead preform 180 may be shapedinto the first lead 110 and attached to the SMD 104 and circuit board102 using the method 200. Also, the second lead preform 182 may beshaped into the second lead 112 and attached to the SMD 104 and circuitboard 102. Moreover, the first and second solder preforms 190, 192 maybe solid, flat, thin pieces of solder material or otherelectrically-conductive joining material. In some embodiments, the firstand second solder preforms 190, 192 may be approximately the same sizeas the first and second terminals ends 130, 132, respectively.

The method 200 may continue at 202, wherein the SMD 104, the first leadpreform 180, the second lead preform 182, the first solder preform 190,and the second solder preform 192 are supported by a fixture 302 of themanufacturing system 300 (FIG. 4). In some embodiments, the fixture 302may be a box-like member with a recess 304 defined therein. The SMD 104may be received centrally within the recess 304. The first and secondlead preforms 180, 182 may be supported within the recess 304 onopposite sides of the SMD 104. The first solder preform 190 may also bereceived within the recess 304 between the first terminal end 130 andthe first lead preform 180. The second solder preform 192 may bereceived within the recess 304 between the second terminal end 132 andthe second lead preform 182. The recess 304 may be shaped and sized suchthat SMD 104, the first lead preform 180, the second lead preform 182,the first solder preform 190, and the second solder preform 192 aretightly arranged (with little-to-no intervening gaps). Also, the recess304 may be sized such that SMD 104, the first lead preform 180, thesecond lead preform 182, the first solder preform 190, and the secondsolder preform 192 may be supported free-standing under the force ofgravity alone on the fixture 302. In some embodiments, the recess 304may have horizontal dimensions that cause SMD 104, the first leadpreform 180, the second lead preform 182, the first solder preform 190,and the second solder preform 192 to be slightly compressed togetherhorizontally.

Furthermore, the method 200 may continue at 204, wherein the SMD 104,the first lead preform 180, the second lead preform 182, the firstsolder preform 190, and the second solder preform 192 are mechanicallyattached and electrically connected. In some embodiments, a temperaturecontrol unit 306 (TCU) may be employed for this purpose. The TCU 306 mayinclude one or more chambers that receives the fixture 302 and thecomponents supported thereon. Once inside, the TCU 306 may provide acontrollable ambient temperature environment for selectively melting andre-solidifying the first and second solder preforms 190, 192. The TCU306 may comprise a reflow oven in some embodiments. In additionalembodiments, the TCU 306 may include a so called “heat pen” that directsheated air at a predetermined location to melt the solder preforms 190,192. Moreover, in some embodiments, the TCU 306 may direct cooled air ata predetermined location to re-solidify the material. In someembodiments, the TCU 306 may be single unit that both melts andre-solidifies the solder preforms 190, 192. Also, in some embodiments,the TCU 306 may include a conveyor (continuous moving belt, automatedarm, etc.) that moves the components from a high-temperature station formelting the preforms 190, 192 and then through a low-temperature stationfor re-solidifying the solder preforms 190, 192. Once re-solidified, thefirst lead preform 180 may be attached to the first terminal end 130 ata first solder joint 194, and the second lead preform 180 may beattached to the second terminal end 132 at a second solder joint 196(FIG. 5).

Moreover, attachment of the lead preforms 180, 182 to the SMD 104 (at204 of the method 200) may include selective control of the rate oftemperature change using the TCU 306. Stated differently, the TCU 306may change temperature (heating and/or cooling) according to apredetermined ramp rate. For example, the TCU 306 may change temperatureselectively according to a ramp rate of less than four degrees Celsiusper second (4° C./s). In additional embodiments, the TCU 306 may changetemperature according to a ramp rate of, at most, two degrees Celsiusper second (2° C./s). Controlling temperature change in this way canprotect the SMD 104 from damage due to thermal shock.

The method 200 may continue at 206, wherein the leads 110, 112 may beshaped. As shown in FIG. 5, the first bend 160 and the second bend 162may be formed using a bending device 308 of the manufacturing system300. The bending device 308 may include a first die 310 about which thepreform 182 may be bent to form the first bend 160. The bending device308 may also include a second die 312 about which the preform 182 may bebent to form the second bend 162. In some embodiments, the bendingdevice 308 may form the first and/or second bends 160, 162 while the SMD104 and preforms 180, 182 are supported in the fixture 302.

Referring back to FIG. 2, the method 200 may include 208, wherein thespacer 108 is attached to the circuit board 102. As shown in FIG. 6, thespacer 108 may be layered and bonded to the mount area 120 between thefirst node 122 and the second node 124. As represented in FIG. 2, thespacer 108 may be attached to the circuit board 102 independently of201-206 of the method 200. In some embodiments, the spacer 108 may bebonded to the mount area 120 using an adhesive (e.g., an epoxy).

Next, the method 200 may proceed to 210, wherein the SMD 104 is attachedto the spacer 108. The SMD 104 may be layered over and bonded to thespacer 108 as shown in FIG. 7. In some embodiments, the SMD 104 may beattached to the spacer 108 via an adhesive (e.g., an epoxy). Then, at212 of the method 200, the leads 110, 112 may be attached to the firstand second nodes 122, 124. As represented in FIG. 7, the boardconnection ends 152 of the leads 110, 112 may be layered over the nodes122, 124, respectively. Then, the TCU 306 may melt and re-solidify toattach the nodes 122, 124 to the board connection ends 152.

The method 200 may also include additional features, includingpre-processing and/or post-processing of the circuit board assembly 100.For example, one or more through-holes 119 and conductive traces 117,121 (FIG. 1) may be formed. The mount arrangement 106 may protect theSMD 104 during these portions of the method as well.

Accordingly, the mount arrangement 106 of the present disclosureprovides robust support and electrical connection for the SMD 104. Themount arrangement 106 also protects the SMD 104 from thermal shockdamage during its useful life and/or during manufacture of the circuitboard assembly 100. The mount arrangement 106 may also facilitatemanufacture of the circuit board assembly 100. The mount arrangement 106may be used in newly designed assemblies 100. The mount arrangement 106may also be used when repairing and replacing SMDs 104 on conventionalcircuit board assemblies 100.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of thepresent disclosure in any way. Rather, the foregoing detaileddescription will provide those skilled in the art with a convenient roadmap for implementing an exemplary embodiment of the present disclosure.It is understood that various changes may be made in the function andarrangement of elements described in an exemplary embodiment withoutdeparting from the scope of the present disclosure as set forth in theappended claims.

What is claimed is:
 1. A method of manufacturing a circuit boardassembly comprising: attaching a flexible electrical lead to anelectronic surface mount device (SMD) with a joining material, includingselectively heating the joining material at a predetermined heating rateand selectively cooling the joining material at a predetermined coolingrate; attaching the SMD to a mount area of a circuit board using aspacer that is interposed between the mount area and the SMD, the spacerspacing the SMD at a distance from the mount area, a coefficient ofthermal expansion (CTE) of the spacer being closer to a CTE of the SMDthan a CTE of the circuit board; and attaching the flexible electricallead to an electrical node of the circuit board.
 2. The method of claim1, wherein the SMD has a first coefficient of thermal expansion (CTE)and the spacer has a second CTE; wherein the second CTE is at least 60%of the first CTE; and wherein the second CTE is at most equal to thefirst CTE.
 3. The method of claim 1, wherein the SMD is a multi-layerceramic chip (MLCC) capacitor.
 4. The method claim 1, wherein the leadis a thin, flexible strap of conductive material, and furthercomprising: attaching, at a first connection, a device connection end ofthe strap to a terminal end of the SMD; attaching, at a secondconnection, a board connection end of the strap to the electrical nodeof the circuit board; and freely extending an intermediate portion ofthe strap between the first connection and the second connection.
 5. Themethod of claim 4, further comprising layering the device connection endof the strap on the terminal end of the SMD; further comprising layeringthe board connection end of the strap on the electrical node; andwherein the device connection end, at the first connection, extendstransversely relative to the board connection end, at the secondconnection.
 6. The method of claim 5, further comprising bending thestrap; and further comprising extending the intermediate portion of thestrap away from the first connection and the circuit board and to returnthe strap toward the second connection with the device connection endextending substantially normal to the board connection end.
 7. Themethod of claim 1, wherein the MLCC and the spacer are made from aceramic.
 8. The method of claim 7, wherein the spacer is made of aluminaceramic (Aluminum Oxide).
 9. The method of claim 8, wherein the lead ismade of annealed copper.
 10. A circuit board assembly comprising: acircuit board with a mount area and an electrical node; an electronicsurface mount device (SMD); a spacer that attaches the SMD to the mountarea of the circuit board and that spaces the SMD at a distance from themount area, a coefficient of thermal expansion (CTE) of the spacer beingcloser to a CTE of the SMD than a CTE of the circuit board; and aflexible electrical lead that extends between and that is electricallyconnected to the SMD and the electrical node of the circuit board. 11.The circuit board assembly of claim 10, wherein the SMD has a firstcoefficient of thermal expansion (CTE) and the spacer has a second CTE;wherein the second CTE is at least 60% of the first CTE; and wherein thesecond CTE is at most equal to the first CTE.
 12. The circuit boardassembly of claim 10, wherein the SMD is a multi-layer ceramic chip(MLCC) capacitor.
 13. The circuit board assembly of claim 10, whereinthe lead is a thin, flexible strap of conductive material; wherein thestrap includes a device connection end that is attached to a terminalend of the SMD; wherein the strap includes a board connection end thatis attached to the electrical node of the circuit board; and wherein thestrap includes an intermediate portion that freely extends between thedevice connection end and the board connection end.
 14. The circuitboard assembly of claim 13, wherein the device connection end of thestrap is layered on the terminal end of the SMD; wherein the boardconnection end of the strap is layered on the electrical node; andwherein the device connection end extends transversely relative to theboard connection end.
 15. The circuit board assembly of claim 14,wherein the device connection end extends substantially normal to theboard connection end; wherein the intermediate portion extends away fromthe device connection end and the circuit board and returns toward thecircuit board and the board connection end.
 16. The circuit boardassembly of claim 15, wherein the intermediate portion curves graduallyfrom the device connection end to the board connection end.
 17. Thecircuit board assembly of claim 10, wherein the MLCC and the spacer aremade from a ceramic.
 18. The circuit board assembly of claim 17, whereinthe spacer is made of alumina ceramic (Aluminum Oxide).
 19. The circuitboard assembly of claim 18, wherein the lead is made of annealed copper.20. A manufacturing system for manufacture of a circuit board assemblycomprising: a fixture that supports an electronic surface mount device(SMD), a flexible electrical lead, and a joining material together; atemperature control unit that selectively controls a temperature of thejoining material while the fixture supports the SMD, the electricallead, and the joining material, the temperature control unit configuredto selectively heat the joining material at a predetermined heating rateto melt the joining material, and to selectively cool the joiningmaterial at a predetermined cooling rate to re-solidify the joiningmaterial, thereby attaching the SMD and the electrical lead; and thetemperature control unit configured to selectively melt and re-solidifya node material of a circuit board while the SMD is attached to a spacerthat is interposed between the SMD and the circuit board, thetemperature control unit configured to selectively heat the nodematerial at the predetermined heating rate to melt the node material,and to selectively cool the node material at the predetermined coolingrate to re-solidify the node material, thereby attaching the electricallead to an electrical node of the circuit board with the spacer spacingthe SMD at a distance from a mount area of the circuit board.